JPS63289975A - Piezoelectric actuator - Google Patents

Abstract

PURPOSE:To obtain a piezoelectric actuator large in its displacement and has no effects of an ambient temperature, by juxtaposing a plurality of piezoelectric laminates at regular intervals and using junction members to couple adjacent parts of the piezoelectric laminates so that their one-sided end parts are shared with each other and further providing them with electrical connections so that they are respectively expanded and contracted contrarily to each other. CONSTITUTION:A plurality of piezoelectric laminates 2a to 2f are juxtaposed at regular intervals, and junction members 25a to 25e are used to couple adjacent parts of the piezoelectric laminates so that their one-sided end parts are shared with each other. Further their adjacent parts of the piezoelectric laminates are provided with electrical connections so that they are respectively expanded and contracted contrarily to each other when a voltage is applied to them. For example, the other end of the piezoelectric laminate 2a and the other end of the piezoelectric laminate 2f are coupled to a fixed member 3 and a movable member 4, respectively. when a voltage is applied to a piezoelectric actuator composed in this way, its state is displaced from (a) to (b) shown in figures. The total amount of displacement for the piezoelectric laminates coupled in number (n) is nX x when the amount of displacement for one piezoelectric laminate is A x.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electro-mechanical conversion device using a piezoelectric element, and particularly to a piezoelectric actuator suitable for an actuator such as a pneumatic control valve.

[Prior Art] Conventionally, electromagnets have been widely used as actuators for pneumatic control valves and the like. In recent years, with the spread of digital circuits and microcomputers, control valves as well as small RFs have come to be controlled by these electronic devices, and control valves that use piezoelectric elements instead of electromagnets have been proposed. . For example, a valve using a piezoelectric laminate made by laminating thin piezoelectric elements as an actuator is published in JP-A-60-211176, and a valve using a bimorph piezoelectric actuator is published in JP-A-60-75776. It is described in. Compared to electromagnets, if a piezoelectric element is used as an actuator, no noise is generated. ■No heat generation. ■There is no sound. ■Low power consumption. ■It has the advantage of being able to miniaturize devices that operate quickly.

[Problems to be Solved by the Invention] As shown in FIGS. 2(a) and (b), the piezoelectric laminate is made up of a large number of thin plate piezoelectric elements 20 stacked together. , internal electrodes 21 are embedded in layers between these piezoelectric elements 20 and are exposed at the end surfaces of the elements. , 22b, and from above the external chamber %
Since 23a and 23b are broken, the internal electrodes 21 are electrically connected to each other in parallel. Piezoelectric element 2o
is polarized in the thickness direction, so the external electrode 2
Electrical terminals 24a, 24b connected to terminals 3a, 23b, respectively
When a voltage is applied between them, they expand in the thickness direction in proportion to the magnitude of the voltage.

Further, by reversing the polarity of voltage application between the electric terminals 24a and 24b, the material contracts in the thickness direction in proportion to the magnitude of the voltage.

Conventionally, such a laminated piezoelectric actuator generates a force of several tens of kilograms, but the amount of displacement is as small as several tens of micrometers, so it has not been possible to put it into practical use alone as an actuator for general control valves. In addition, due to the voltage resistance of the element and the connection of the electrodes, the limit is about several 100V due to the G, M type, the number of laminated elements is also limited due to the structure, and the large shape in the length direction is difficult for control valves. This means that the actuator cannot be made smaller.

As a solution to this problem, Japanese Patent Application Laid-Open No. 60-211176 has a built-in hydraulic pump as a displacement magnification mechanism to magnify the axial displacement caused by the piezoelectric laminate, since the amount of displacement is small when the piezoelectric laminate is used alone. A valve having the following is disclosed.

On the other hand, the bimorph type piezoelectric actuator used as an actuator in the electronic valve of Utility Model Application No. 60-75776 has a displacement of several 100 μm, but the generated force is several Lo.
It is as small as g. Therefore, even when controlling several kg/crd of compressed air, if the valve diameter is not sufficiently small, the valve cannot operate and can only be used for valves with small flow rates.

In this way, when using conventional piezoelectric actuators for control valves, whether they are stacked type or bimorph type,
There were problems in that the cross-sectional area of the flow path of the valve could not be made large, and that the operation became unstable due to thermal displacement caused by changes in ambient temperature.

In order to solve the above-mentioned problems, the purpose of the present invention is to create a structure in which piezoelectric laminates are combined,
-7 It is an object of the present invention to provide a laminated piezoelectric actuator that can increase the amount of displacement and is not affected by ambient temperature.

[Means for solving problems] FIG. 1 is a diagram showing the basic configuration of a piezoelectric actuator according to the present invention, in which a plurality of (six in this figure) piezoelectric laminates 2a, 2b, 2c, . , , 2f are arranged in parallel with a gap, and adjacent piezoelectric laminates are connected to a contact member 25a.
, 25b, . . . , 25e are connected to each other so as to share one end.

Further, adjacent piezoelectric laminates are electrically connected so that when a voltage is applied to each, the voltages are opposite to each other.

That is, the piezoelectric laminates 2a, 2c, and 2e are configured to contract in the length direction, and the piezoelectric camellia footwear 2b, 2d, and 2f are configured to expand in the opposite direction.

The other end of the piezoelectric laminate 2a is attached to the fixing member 3, and the piezoelectric laminate 2f is attached to the fixing member 3.
The other end is connected to the movable member 4.

[Operation] In the piezoelectric actuator configured in this way,
When voltage is applied, the state shown in Fig. 1(a) changes to Fig. 1(b).
Displaced to the state of. That is, the piezoelectric laminate 2a connected to the fixing member 3 shrinks by a certain amount in the length direction of the piezoelectric elements stacked in the thickness direction, and the adjacent piezoelectric laminate 2b connected to this piezoelectric laminate 2a shrinks conversely. Stretch 9 In this way, n pieces of piezoelectric 'f? When the footwear body is connected, if the displacement amount for one piezoelectric laminated tree is Δχ, the total displacement amount is n×Δχ. When six piezoelectric laminates are used as shown in the figure, a displacement amount six times that of one piezoelectric laminate can be obtained. Furthermore, since the piezoelectric laminates are arranged in parallel, the length in the longitudinal direction is the same as that of a single piezoelectric laminate. Although adjacent piezoelectric laminates simultaneously expand or contract by the same amount in response to changes in ambient temperature, the positional relationship between the fixed member 3 and the movable member 4 is not affected by thermal changes.

[Example] An example is shown in which FIG. 3(a) is a cross-sectional view taken along the axis, and FIG. 3(b) is a bottom view of the cut piece, with a partial cross section shown. There is.

2a, 2b, 2c, , , 2f have the same length,
It is a tubular piezoelectric laminate with different diameters.

As shown in FIG. 2(C), these piezoelectric laminates are made by laminating and integrating a large number of annular piezoelectric elements 20, and an annular internal electrode 21 is arranged between these piezoelectric elements 20 in a layered manner. Every other internal electrode 21 that is embedded in the device and exposed at the end face of the element is covered with insulators 22a and 22b, and external electrodes 23a and 23b are applied from above. Therefore, each internal electrode 21 is electrically connected in parallel to each other.

Since the piezoelectric element 20 is polarized in the thickness direction, the electric terminals 2 connected to the external electrodes 23a and 23b, respectively,
When a voltage is applied between 4a and 24b, in the thickness direction,
That is, the length of the annular piezoelectric laminate or the electrical terminals 24a, 24b
By changing the polarity of the voltage applied between them and connecting them, they contract in the opposite direction.

Such tubular piezoelectric laminates 2a, 2b, 2c.

, , 2f are arranged coaxially with a gap between them, and adjacent piezoelectric laminates are connected to annular contact members 25 a, 25 b, .
, , 25e so that they share one end.

With this structure, the piezoelectric actuator 1
can be made even more mechanically stable and strong. Adjacent piezoelectric laminates are electrically connected so that the polarities of the voltages are opposite so that when a voltage is applied to each piezoelectric layer, the expansion and contraction are opposite to each other. That is, the piezoelectric laminates 2a, 2c
, 2e contract in the length direction, and the piezoelectric laminates 2b, 2d, 2
f is configured to extend. A fixed member 3 is fixed to the other end of the piezoelectric laminate 2a, and a movable member 4 is fixed to the other end of the piezoelectric laminate 2f. The fixed member 3 and the movable member 4 are on the same plane in the state shown in FIG. 3(a) when no voltage is applied, and this serves as a reference plane for the amount of displacement.

Since the tubular piezoelectric laminates mutually expand and contract by a predetermined amount of displacement, the movable member 4 can be displaced with respect to the fixed member 3 by six times the amount of displacement of one piezoelectric laminate.

FIG. 4 is a sectional view of a control valve using the piezoelectric actuator of the present invention. 3 is a housing of a control valve V, and a tubular valve body 4 is slidably provided on the axis of the housing 3. A valve seat 5 and a valve seat 6 are disposed at the upper and lower parts of the housing 3, respectively, so as to face both ends of the valve body 4, and when the valve body 4 comes into contact with one valve seat, the valve seat 6 touches the other valve seat. It's starting to move away from. The chamber 7 with the valve seat 5 communicates with the inboard 9, and the chamber 8 with the valve seat 6 communicates with the outboard 10. Further, a flow path is formed in the valve seat 6 in the axial direction and communicates with the exhaust port 11 . The tubular piezoelectric actuator 1 of the present invention has a housing 3
The valve body 4 is disposed coaxially within a cylindrical chamber 12 formed in the center of the valve body 4 . The fixed side is fixed to an annular protrusion 3a of the housing 3, and the movable side is fixed to a flange 4a provided on the valve body 4. A spring 13 is disposed between the flange portion 4a of the valve body 4 and the upper surface of the chamber 12, and is biased to bring the valve body 4 into contact with the valve seat 5.

In the state shown in FIG. 4 when the piezoelectric actuator 1 is not operating, the valve seat 5 is closed and the valve seat 6 is open, so the inboard 9
The outboard 10 and the exhaust port 11 are in communication with each other.

Next, when a voltage is applied to the piezoelectric actuator 1, the piezoelectric actuator enters the state shown in FIG. 3(C), and the valve body 4 is pushed up against the spring 13 and comes into contact with the valve seat 6. Therefore, the inboard 9 communicates with the exhaust port 11 via the flow path in the valve 4, and the outboard 10 and the exhaust port 11 are cut off.

By moving the tubular valve body 4 using the piezoelectric actuator 1 in this way, the flow path can be cut in three directions with relatively light force. Therefore, due to the large force and large displacement of the piezoelectric actuator 1, it has become possible to increase the cross-sectional area of the flow path of the valve. It can be made into a 2-way valve by blocking it with an inboard 9 blind plug, and in addition to 0N-OFF control, it can also be used as a flow rate control valve because the amount of displacement can be changed by changing the applied voltage of the piezoelectric actuator and the cross-sectional area of the flow path can be controlled. Can be used. Since tubular piezoelectric laminates with different diameters are arranged coaxially, the length on the axis is the same as the length of one piezoelectric laminate, so it can be made compact. Furthermore, by disposing piezoelectric actuators that use flat piezoelectric elements (as shown in FIG. 1), which is the basic structure of the present invention, instead of a tubular piezoelectric laminate on both sides of the valve body 4, the width of the control valve can be made thinner. It is possible to increase the degree of integration of control valves when they are placed in the same space.

Note that the piezoelectric actuator described above can be used to control weak control signals from an external microcomputer by incorporating a drive circuit in the control valve to convert weak control signals from an external microcomputer into high-voltage control signals that drive the piezoelectric element. Can be directly controlled by control signals.

FIG. 5 shows another embodiment of the piezoelectric actuator according to the present invention. The joining members 25a, 25c form a pair of two piezoelectric laminates of equal length electrically connected so that expansion and contraction are opposite to each other.

, , 25 are connected. Furthermore, each set of piezoelectric laminates 2A, 2B, ..., 2F having different lengths is connected to a joining member 25.
b, 25d, , , 25j. If a voltage is individually applied to each set of piezoelectric laminates with such a configuration, different amounts of displacement can be obtained. In the case shown in this figure, since six sets are arranged, the amount of displacement can be controlled by a 6-bit digital signal, and therefore it can be used as a flow rate control valve, etc.

[Effects of the Invention] As explained above, the piezoelectric actuator of the present invention has a plurality of piezoelectric laminates arranged in parallel with a gap therebetween such that adjacent piezoelectric laminates share one end with each other. Since they are connected by a joining member and are electrically connected so that expansion and contraction are opposite to each other, it is possible to obtain a large displacement even though the axial dimension is large compared to the conventional laminated type.
In addition, even if each piezoelectric laminate undergoes thermal displacement due to changes in ambient temperature, the movable members do not change relative to the fixed members, so when used in control valves, the cross-sectional area of the flow path can be increased and the In addition, since there is no need to provide a displacement amplifying mechanism, the device can be made smaller.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the basic configuration of the present invention, FIG. 2 is a perspective view of a piezoelectric laminate used in the piezoelectric actuator of the present invention,
Fig. 3 is a diagram showing an embodiment, Fig. 3(a) is a sectional view taken along the axis, and Fig. 3(b) is a bottom view of Fig. 3(a), showing a partial cross section. ing. FIG. 3(c) is a diagram showing a state of movement. FIG. 4 is a cross-sectional view of a control valve that is an example of the application of the present invention.
FIG. 5 is a diagram showing another embodiment. 2a, 2b, 2C...Piezoelectric laminate 25a
, 25b, 25c...Joining member 3...
・・・・・・・・・Fixing member 4・・・・・・・・・
・・・・・・・・・Movable member patent applicant: CKD Co., Ltd. No. 1 L'J Uta- No. 21 (C) Fig. 4 No. 5N

Claims (3)

[Claims] (1) Adjacent piezoelectric laminates of a plurality of piezoelectric laminates arranged in parallel with a gap are connected by a joining member so as to share one end with each other, and the expansion and contraction are opposite to each other. A piezoelectric actuator characterized in that it is electrically connected to (2) The piezoelectric actuator according to claim 1, wherein the piezoelectric laminates are coaxially arranged tubular bodies having different diameters. (3) A plurality of pairs of piezoelectric laminates having the same length and opposite expansion and contraction are combined, and each set of piezoelectric laminates has a different length. piezoelectric actuator.